Moss and algae on roof?
I noticed some moss and algae stains on the north side of the roof. Does this need action, and if so, how soon?
Located in Madison, WI, climate zone six. I’m mainly concerned with the short roof, but there’s some moss on the main roof as well, so I included one photo of it in the album.
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Tide with Bleach sprinkled on the shingles and left for several days will kill the moss without damaging the roof. You may have to remove the dead moss by hand rubbing it with a leather work glove. Several shingle manufacturers suggest this approach in their literature.
You can install strips of zinc along the roof ridges to keep moss from re-growing--at least where rainwater carries the zinc ions. Here's one of many products: http://www.zincshield.com/home.html.
I used "Wet & Forget" and it worked well. So did sprinkling powdered brass along the ridge.